Problem: $d(n) = -5 \left(\dfrac{1}{2}\right)^{n - 1}$ What is the $3^\text{rd}$ term in the sequence?
This is an explicit formula. All we have to do is plug $n=3$ in the formula to find the $3^\text{rd}$ term. $\begin{aligned} d({3}) &=-5\left(\dfrac12\right)^{{3} - 1} \\\\ &= -\dfrac54 \end{aligned}$ The $3^\text{rd}$ term is $-\dfrac54$.